Per (beta and gamma substituted alkylene)mono-and di-tin compounds and the preparation thereof



United States Patent This invention relates to a novel method for theproduction of organotin compounds and to the novel products thereof.More particularly, it relates to the production of organotin compoundswherein the organic moieties possess functional group substituents.

Numerous examples are available in the art of organotin compoundswherein the tin moiety possesses a multiplicity of hydrocarbylsubstituents, for example, tetramethyltin and tetraphenyltin. Little isknown, however, of organotin compounds with non-hydrocarbyl organicsubstituents. Tomilov et al., Zhur. Priklad. Khim., 32, 2600 (1959),report the formation of tetrakis(fi-cyan0- ethyl)tin by electrolysis ofstrongly basic, concentrated, aqueous solutions of acrylonitrile in thepresence of a tin cathode. At a pH of 13-14 and a current density below2000 amp/m e.g. 200 amp/m2, the tetrakis(fl-cyanoethyl)tin is produced,together with substantial amounts of by-products, particularlybis(,B-cyanoethyl)ether. The yield of B-cyanoethyl tin compound obtainedby Tomilov et al. is comparably low, and considerable acrylonitrile islost through by-product formation, which by-products render morediflicult the recovery of the desired organotin compound. It would be ofadvantage to provide a more satisfactory method for the production ofsuch organotin compounds.

It is an object of the present invention to provide an improved methodfor the production of organotin compounds having organic moietiespossessing non-hydrocarbyl substituents and the novel compounds producedthereby. A further object is to provide a process for the production oforganotin compounds wherein each tin substituent is a non-hydrocarbylorganic moiety. A more particular object is to provide a process for theproduction of per(,B-cyanoethyl)monoto di-tin compounds and relatedfi-substituted compounds. A specific object is to provide a process forthe production of per(,B-carboxyethyl) monoto di-tin.

It has now been found that these objects are accomplished by the processof electrolyzing aqueous solutions of acrylonitrile in the presence of atin cathode under controlled conditions of cathode reference potentialand basicity of the electrolyte solution, followed by subsequentchemical transformation of the per(/3-cyanoethyl) monoto di-tin product.The process of the invention is adaptable for the production oftetrakis(fi-cyanoethyl)tin and related monotin compounds, oralternatively for the production of the novelhexakis(fi-cyanoethyl)ditin and related ditin products, which productionoccurs in high yield with little attendant formation of by-products. TheB-cyanoethyl tin compounds have been found to be surprisingly resistantto hydrolysis of the carbon-tin or tin-tin linkages, and are readilyconverted to other novel organotin compounds.

The process of the invention therefore comprises electrolyzing mildlybasic aqueous solutions of acrylonitrile under controlled conditions toproduce tetrakis(fl-cyanoethyl)tin or alternativelyhexakis(;3-cyanoethyl)ditin and subsequently, if desired, performingchemical transformations upon the cyano moieties thereby producingrelated derivatives.

The electrolyte solution employed in the process of the inventioncomprises an aqueous solution of acrylonitrile,

3,332,970 Patented July 25, 1967 "ice optionally containing miscibleco-solvent, to which has been added sufficient base to render thesolution mildly basic. The optimum concentration of acrylonitrile in theelectrolyte solution will largerly be determined by the type of productthat is desired, as the production of tetrakis(fi-cyanoethyl)tin isfavored by comparably high con centrations of acrylonitrile, whereashexakisUi-cyanoethyl)ditin is the predominant product when comparablylow acrylonitrile concentrations are employed. Suitable concentrationsof acrylonitrile in the electrolyte solution vary from about 3% byweight to about 30% by weight based upon the total weight of electrolytesolution. For the production of the hexakis(B-cyanoethyl)ditin,acrylonitrile concentrations from about 5% by weight to about 15% byweight on the same basis are preferred, although the formation oftetrakis(B-cyanoethyDtin is preferably accomplished through utilizationof electrolyte solutions containing from about 17% by weight to about25% by weight on the same basis of acrylonitrile.

The principal solvent employed in the electrolyte solution is, ofcourse, water, and it is Within the contemplated scope of the invention,particularly when the ditin product is desired, to employ no additionalco-solvent. When higher concentrations of acrylonitrile are desired, asin the production of tetrakis(B-cyanoethyhtin, co-solvent is suitablyutilized to increase the solubility of the acrylonitrile in theelectrolyte solution. Co-solvents that are satisfactorily utilized aremiscible with water, are polar solvents, that is, contain an unevencharge distribution, and are unaffected by the electrolytic reactionconditions as well as being inert to the acrylonitrile reactants and theorganotin compounds produced therefrom. Illustrative co-solvents thatare suitably employed include ethers such as tetrahydrofuran, dioxaneand dioxolane; N,N-dialkyl carboxylic acid amides such asdimethylformamide, diethylformamide, N-methylpyrrolidinone andN,N-dimethylacetamide; and nitriles such as acetonitrile. Whenco-solvent is employed, amounts of co-solvent up to about 30% by weightof the total electrolyte solution are satisfactory, althoughconcentrations up to about 25% by weight on the same basis arepreferred.

It has been found that the control of the pH of the electrolytesolution, defined as the negative logarithm of the molar hydrogen ionconcentration thereof, is a critical factor in the process of theinvention, particularly with regard to minimizing the formation ofby-products. Although the process is operable at a high pH, e.g., overabout 9.5, production of larger percentages of undesirable by-productsis concomitant with an increase in pH. It is required, however, that theelectrolyte solution be basic, that is, have a pH greater than 7. Bestresults are obtained when the pH of the solution is maintained betweenabout 7.5 and about 9.

The pH of the electrolyte solution is controlled by the addition ofbase. By the term base as employed herein is meant a material capable ofdonating an electron pair or alternatively a material whose aqueoussolutions have a pH greater than 7. Suitable bases are soluble in waterto the extent necessary to give the desired pH, and at theconcentrations employed are inert to the acrylonitrile reactant and theproducts produced therefrom. Typical bases include alkali metal andalkaline earth metal hydroxides such as sodium hydroxide, potassiumhydroxide and barium hydroxide as well as the corresponding oxides,e.g., sodium oxide, calcium oxide and lithium oxide; alkali metalcarbonates and bicarbonates such as sodium bicarbonate, potassiumbicarbonate, sodium carbonate and lithium carbonate, alkali metalalkoxides such as sodium methoxide, potassium tert-butoxide, lithiumisopropoxide and sodium ethoxide; and salts of comparably strong basesand comparably weak acids such as sodium acetate, potassium propionate,tetramethylammonium p-toluenesulfonate, methyltri-n-butylphosphoniumnaphthalenesulfonate and tetramethylammonium sulfate. The amount of basethat is added to the electrolyte solution will be dependent upon theparticular base that is employed, as the absolute amount of base is notcritical except in so far as it determines the pH of the electrolytesolution. Sufiicient base is added to give the solution the desired pH.Best results are obtained when the base is to be employed is an alkalimetal bicarbonate, particularly sodium bicarbonate, and an approximately5% by Weight aqueous solution thereof gives a suitable pH of about 8.5.

In the electrolysis reaction, the cathode of the electrolysis cell iscomposed of tin. Although alloys of tin with other metals, particularlyless active metals, may be employed it is preferred to utilize a cathodethat is substantially pure tin. The anode of the electrolysis cell isnot affected by the electrolysis process and therefore is suitablyprepared from any convenient inert material capable of conducting theelectric current and non-reactive with the aqueous solution. Typicalanode materials include platinum, nickel, graphite, tin, lead or thelike. Preferred are anodes prepared from platinum or graphite.

The electrolysis process of the invention comprises charging theelectrolyte solution to the electrolysis cell wherein the tin cathodeand the anode are placed. For purposes of control of the cell referencepotential, a standard electrode, typically a saturated calomel electrode(S.C.E.) such as is described in Weissberger, Physical Methods, NewYork, Interscience Publishers, Inc., 1960, vol. I, Part IV, isintroduced into the cell in the vicinity of the cathode and connected tothe source of the direct electric current and to the cathode in aconventional manner so that the reference potential of the cathode canbe determined. It has been found that the reference potential of thecathode is a critical factor in the production of the B-cyanoethyl tincompounds. During the course of the electrolysis, as acrylonitrile isremoved from the electrolyte solution through the formation of organotincompound, the reference potential of the cathode must be increased if aconstant current density is maintained. Rather than alter the cathodereference potential to maintain a constant current density, it has beenfound desirable to maintain a constant cathode reference potential andallow the current to vary if required. In one preferred modification ofthe process of the invention, however, acrylonitrile is continuouslyadded to the cell to replace that lost by organotin compound formation,and the current density also remains substantially constant. Cathodereference potentials from about 1.6 volt to about 2.0 volts vs. thesaturated calomel electrode are satisfactory, although a cathodereference potential of from about l.7 volt to about -l.9 volt (vs.S.C.E.) is preferred.

The electrolysis process is conducted at moderate temperatures, andtemperatures that are above the freezing point of the electrolytesolution but below about 50 C. are satisfactory. Best results areobtained when temperatures from about C. to about 40 C. are employed. Asthe reaction temperature is a factor in determining the solubility ofthe acrylonitrile in the electrolyte solution, the reaction temperatureis a factor in the determination of the major reaction product. When theproduction of hexakis([3-cyanoethyl)ditin is desired, the lower reactiontemperatures, e.g., about 5 C. to C., are suitably utilized, whereas theformation of tetrakis(;3-cyanoethyl) tin is favored by the use ofcomparably higher reaction temperatures, for example, from about C. toabout 30 C.

Subsequent to the electrolysis process, the ,B-cyanoethyl tincompound(s) are separated and recovered by conventional methods such asfractional distillation, selective extraction, crystallization and thelike.

The products of the electrolysis procedure are ,tetrakis-(Bcyanoethyl)tin, hexakis(,B-cyanoethyDdi-tin or mixtures thereof,depending largely upon the reaction conditions employed. Genericallythese products are represented by the formula wherein n has thepreviously stated significance and X is aminomethyl, halocarbonylwherein the halogen is halogen of atomic number from 17 to 35,preferably chlorine,

0 (.OR and JNR wherein R is hydrogen or alkyl of from 1 to 8 carbonatoms.

In the above formula, when X represents aminomethyl, the products areper('y-aminopropyl)rnonoto di-tln compounds prepared by reduction of thecorresponding [3- cyanoethyl group. The reduction is accomplished by avariety of methods, among which is catalytic reduction with molecularhydrogen. The ,B-cyanoethyl tin compound is contacted with molecularhydrogen in the presence of a hydrogenation catalyst, e.g., a transitionmetal, particularly a transition metal of Group VIII of the PeriodicTable such as nickel, palladium, platinum or rhodium, as well as oxidesthereof; or a mixed oxide catalyst such as copper chromite. Thecatalytic reduction is typically effected in the substantial absence ofsolvent or in the presence of an inert solvent, e.g., ethers,hydrocarbons and the like, at somewhat elevated temperatures, e.g., fromabout 50 C. to about 150 C., and preferably at superatmosphericpressures of hydrogen, for example, from about 2 to about 20atmospheres. An alternative method of effecting reduction of the cyanogroup to the aminomethyl group comprises the use of a chemical reducingagent such as lithium aluminum hydride, generally as a solution orsuspension in an inert, anhydrous diluent which frequently is an ether.By either method, the production of per('y-aminopropyl)monoto di-tin iseffected in good yield with little or no carbon-tin or tin-tin cleavage.

The compounds of the above formula wherein X is carboxy are produced byalkaline hydrolysis of the corresponding ,B-cyanoethyl tin compoundfollowed by acidification of the resulting carboxylate salt. Bases thatare suitably employed in the alkaline hydrolysis are strong bases,particularly alkali metal and alkaline earth metal hydroxides such assodium hydroxide, potassium hydroxide calcium hydroxide, bariumhydroxide and the like, as well as corresponding alkali metal andalkaline earth metal oxides, e.g., sodium oxide. The hydrolysis istypically conducted in aqueous or aqueousalcoholic solution as bycontacting the ,B-cyanoethyl tin compound with an aqueous solution ofthe base and maintaining the resulting mixture at a somewhat elevatedtemperature, e.g., from about C. to about C., until reaction iscomplete. Subsequent to hydrolysis, the product solution is neutralizedwith any convenient acidic material to liberate the free carboxylicacid.

The per(B-carboxyethyl)monoto di-tin compounds are suitably employed asstarting materials for the production of the corresponding acid halides,that is, the com pounds of the above depicted formula wherein X ishalocarbonyl. Preferred per (fl-halocarbonylethy1)-monoto '.di-tincompounds are those wherein the halogen is halogen of atomic number from17 to 35, that is, the middle halogens chlorine and bromine, andparticularly preferred are those halocarbonyl compounds wherein thehalogen is chlorine. The acid halides are prepared by treating theperQB-carboxyethyDmonoto di-tin compounds with an inorganic acid halidesuch as thionyl chloride, phosphorus trichloride, phosphoruspentachloride or the like when acid chlorides are desired as theproduct, or with corresponding inorganic bromides when the production ofacid bromides is desired. The reaction is conducted in the presence ofan inert reaction medium or alternatively may be effected by merelycontacting the p-carboxyethyl tin compound with the inorganic acidhalide in the absence of solvent. The reaction is preferably conductedunder anhydrous conditions to minimize the hydrolysis of the inorganicreactant or the fl-halocarbonylethyl tin product.

The production of per(fi-carboalkoxyethyl)monoto ditin compounds isachieved by one of several methods. the fl-cyanoethyl tin compounds ofthe invention are converted to the corresponding ,B-carboalkoxyethylderivatives by acidic hydrolysis in alcoholic solution. Alcoholspreferably employed for ester formation are monohydric alcohols havingfrom 1 to 8 carbon atoms. Best results are obtained when the alcoholemployed is an alkanol, particularly a primary alkanol such as methanol,ethanol, propanol, isobutanol, Z-ethylhexanol, n-octanol or the like.The optimum amount of alcohol to be employed will depend upon thefunctionality of the 6- cyanoethyl tin compound, i.e., whether thetetrakis or the hexakis derivative is employed. Satisfactory results aregenerally obtained when substantially stoichiometric amounts of alcoholare utilized, that is, a ratio of moles of alcohol to moles of cyanomoiety of about 1:1. The hydrolysis and ester formation is catalyzed bysmall amounts of acid, preferably a strong acid. Exemplary acids includeinorganic acids such as hydrochloric acid, phosphoric acid and sulfuricacid; organic acids including sulfonic acids such as p-toluenesulfonicacid and methanesulfonic acid and carboxylic acids such astrichloroacetic acid; and acidic resinous materials known as cationicexchange resins. In an alternate and frequently preferred modification,the p-carboalkoxyethyl tin compounds are produced by reaction of thealkanol with the B-halocarbonylethyl compounds previously described.Such a process is typically conducted by mixing the acid halidederivative and the alkanol, preferably in the presence of a hydrogenhalide acceptor, e.g., tertiary amines such as pyridine ortriethylamine. The reaction occurs readily at ambient temperature orabove. When the production of fl-carbomethoxyethyl tin compounds isdesired, a somewhat special situation exists. In addition to thepreparative methods previously described, reaction of fl-carboxyethyltin compounds with diazomethane results in efficient production of themethyl ester. This esterification procedure is customarily conducted inan inert reaction medium, typically an ether such as diethyl ether,dioxane, or tetrahydrofuran. Due to the known reactive character of thediazomethane, the reaction is preferably conducted at room temperatureor below, and by adding a solution of diazomethane in the reactionmedium in increments to a solution or suspension of the B-carboxyethyltin reactant.

The compounds of the above-depicted formula wherein X represents thegroup wherein R has the previously stated significance are amides, andare conveniently produced by reaction of the fl-halocarbonylethyl tincompounds previously described with ammonia to produce amide derivativeswherein both R groups represent hydrogen, with primary amides to produceN-alkylamides wherein one R group represents alkyl of from 1 to 8 carbonatoms, and with secondary amines to produce N,N-dialkylamides.Illustrative amines include methylamine, ethylamine, octylamine,diethylamine, methylhexylamine and the like. The preferrednitrogen-containing reactant is however ammonia as the preferred amideproduct is per(fi-carbamidoethyl)monoto di-tin.

The products of the process of the invention are useful in a variety ofapplications. Due to the number of types of functional groups which areproduced, a variety of other useful derivatives, e.g., polyamides andpolyesters and secondary and tertiary amines may be prepared therefrom.The amino and carboxy derivatives are useful as epoxy curing agents andthe organotin compounds are additionally useful as corrosion inhibitorsin lubricating oils, anti-knock additives in gasolines and anti-foulingagents for explosives and propellants. Additionally the organotincompounds find utility in the area of agricultural chemicals,particularly as molluscicides.

To further illustrate the novel process of the invention and the novelcompounds produced thereby, the following examples are provided. Itshould be understoodthat the details thereof are not to be regarded aslimitations, as they may be varied as will be understood by one skilledin this art.

Example I A cylindrical electrolysis cell of approximately 750 ml.capacity was fitted with a close-fitting cylindrical tin cathode of 200cm. inside surface area. A platinum anode was supported so that it wasconcentric with the tin cathode and a reference electrode was placed inthe vicinity of the cathode.

The cell was charged with a mixture of 375 ml. of 5% by weight aqueoussodium bicarbonate solution, 125 ml. of acetonitrile and 53 g. ofacrylonitrile. The pH of the solution was 8.5. The cathode potential wasset at -l.85 volts vs. S.C.E. and the reaction vessel was cooled withwater to maintain a temperature below 30 C. At the end of 16 hours, thereaction was terminated and the tin cathode was found to have lost 15.0g.

The electrolyte solution was extracted with four ml. portions ofchloroform. The combined extracts were dried and filtered and thendistilled, initially at atmospheric pressure and then at reducedpressure. Gas-liquid chromatographic analysis of the low-boilingcomponents indicated the presence of 18.61 g. acrylonitrile, 4.2 g. ofpropionitrile as well as acetonitrile and chloroform. Also obtainedduring distillation were 1.3 g. of bis(ficyanoethyl)ether and 0.7 g. ofadiponitrile.

A dark distillation residue of 37.5 g. was obtained which wascrystallized by cooling from chloroform to afford 34.1 g.tetrakis(B-cyanoethyDtin, M.P. 22-24 C. This infrared and nuclearmagnetic spectra were consistent with the above formula. The conversionof acrylonitrile to tetrakis(,B-cyanoethyDtin was 40.9% and the yield oftetrakis(,B-cyanoethyl)tin was 63% when based upon acrylonitrileconverted and 80.2% when based on tin loss from the cathode.

Example II The procedure of Example I was repeated employing ml.dimethylformamide in place of the acetonitrile. The reaction was allowedto proceed 17 hours at which time the weight loss of the cathode was16.1 g. By a similar work-up procedure, a recovery of 21.4 g. ofacrylonitrile was obtained and 33.7 g. of tetrakis( 3-cyanoethyl)tin,which represented a 67.6% yield based upon acrylonitrile converted and a74% conversion based on tin. The conversion of acrylonitrile totetrakis(}8-cyanoethyl)tin was 40.4%.

Example III To a cell containing a 50 cm. rectangular (one face) tincathode and a platinum anode is added 250 m1. of aqueous 0.5 N sodiumhydroxide solution and 53 g. of acrylonitrile. A reference electrode wasplaced in the vicinity of the cathode and a current of 1.0 amp waspassed such that the current density on the working face of the cathodewas 200 amp/m. throughout the electrolysis. Initially it was found thatthis corresponded to a potential of 1.2 volt (vs. S.C.E.) althoughduring the course of the electrolysis the reference potential increasedto 1.87 volt (vs. S.C.E.). The cross cell voltage was initially 4.2volts and the reaction temperature was maintained at 10 C.18 C. Duringthe electrolysis, acrylonitrile was added to the electrolyte at a rateof approximately ml./ hr. At the end of 6.5 hours the electrolysis wasterminated and the cathode was found to have lost 7.2 g.

The contents of the cell was found to consist of three phases. The upperphase was principally unreacted acrylonitrile, the middle phase was asolution of acrylonitrile in aqueous sodium hydroxide and the bottomlayer was a heavy, yellow oil. The whole was extracted with chloroformand fractionally distilled to give, inter alia, 97.8 g. ofacrylonitrile, 4.4 g. of propionitrile, 0.35 g. of adiponitrile and 11.6g. of bis(fi-cyanoethyl)-ether, B.P. 114-117 C. at 1 mm., which wasidentified by the infrared and nuclear magnetic resonance spectra.

Analysis calc., percent wt.: C, 58.0; H, 6.45; N, 22.6. Found: C, 57.9;H, 6.6; N, 22.1.

Also obtained was a dark residue which upon crystallization fromchloroform (Dry Ice cooling), afforded 17.26 g. of colorless crystals,M.P. 2324 0. Infrared and nuclear magnetic resonance spectra indicatedthe material was tetrakisUi-cyanoethyl)tin.

Analysis calc., percent wt.: C, 43.0; H, 4.48; N, 16.7; Sn, 35.4. Found:C, 42.7; H, 5.0; N, 16.1; Sn, 35.1.

Under the highly basic conditions of this experiment, the yield oforganotin based upon acrylonitrile converted was 31.1%. The conversionof acrylonitrile to tetrakis(,B- cyanoethyl)tin was 8.25%.

When the above experiment was repeated employing an initial addition of132.5 g. of acrylonitrile only, the conversion to organotin compound ofthe acrylonitrile after 6 hours was 9.8% and the yield of tetrakis(,B-cyanoethyl) tin based on acrylonitrile converted was 31.4%.

When the above experiment was repeated except that a controlled cathodepotential of 1.9 volt (vs. S.C.E.) was maintained rather than constantcurrent density of 200 amp/m. the conversion of acrylonitrile toorganotin compound after 5 hours was 13.8% and the yield of organotinproduct, 29.75 g., was 43% based on acrylonitrile converted. The amountof bis(,B-cyanoethyl)ether produced was 9.1 g.

Example IV The procedure of Example I was followed to electrolyze asolution consisting of 320 ml. of 5% by weight aqueous sodiumbicarbonate, 80 ml. of dimethylformamide and 212 g. acrylonitrile. Atthe end of 16 hours, 46.95 g. had been lost by the tin cathode. Duringthe work-up, 83.02 g. of acrylonitrile was recovered and 114.9 g. oftetrakisQS- cyanoethyl)tin was obtained which represented a yield of73.6% based upon the acrylonitrile converted and a yield of 86.5% basedupon the tin lost by the cathode.

Example V The procedure of Example I was followed to electrolyze asolution consisting of 500 g. of 5% by weight aqueoustetramethylammonium p-toluenesulfonate and 53 g. of acrylonitrile. Thesolution had a pH of 8.5. At the end of 16 hours, the tin cathode weighthad decreased 17.8 g. Upon work-up, 16.54 g. of acrylonitrile wasrecovered and 35.8 g. of tetrakis(,B-cyanoethyl)tin was obtained whichrepresented a 62.1% yield based upon converted acrylonitrile and a 71.1%yield based upon tin. When the concentrated filtrate from thetetrakis(,8-cyanoethyl) tin crystallization was allowed to stand, 1.25g. of clear crystals of hexakis(,8-cyanoethyl)ditin, M.P. 109-110 C.,were obtained.

Exam ple VI In an electrolysis cell similar to that described in ExampleI, a solution of 550* ml. of 5% by weight aqueous sodium bicarbonate and53 g. of acrylonitrile was electrolyzed at a reference potential of 1.9volt (vs. S.C.E.) for 15 hours while the temperature was kept below 15C. During this time, the tin cathode lost 14.15 g. and solid appeared inthe electrolyte. The solid, 9.5 g., was filtered from the electrolyteand set aside.

Subsequent to extraction of the electrolyte solution with four 100 ml.portions of methylene chloride, the low boiling components of thecombined extract were removed by distillation. Upon cooling of theresidue, an additional 22.1 g. of crystals were obtained which wereremoved by filtration and also set aside. The filtrate was treated with25 ml. of benzene and allowed to stand at room temperature for 6 daysduring which time an additional 4.5 g. of crystals were obtained. Thetotal solids were recrystallized from chloroform to give 32.1 g. ofhexakis(,8-cyanoethyl)ditin, M.P. 111.5 C. Evaporation of the benzenefrom the filtrate gave 4.1 g. of yellow oil, from which 0.86 g. oftetrakisQS-cyanoethyl)tin Was obtained.

The infrared and nuclear magnetic resonance spectrum of the ditincompound were consistent with the above formula.

Analysis calc., percent wt.: C, 38.4; H, 4.28; N, 14.95; Sn, 42.2.Found: C, 38.4; H, 4.3; N, 14.5; Sn, 41.6.

The conversion of acrylonitrile to the ditin compound was 34.4% andbased upon the acrylonitrile converted the yield was 70.2%. The yield ofhexakis (B-cyanoethyl) ditin based on cathode weight loss was 95.5%.

Example VII The procedure of Example VI was repeated employing 106 g. ofacrylonitrile in the electrolyte solution. The weight lost from thecathode was 15.3 g., and upon workup, 20.7 g. of acrylonitrile wasrecovered. From the product mixture was recovered 2.8 g. of tetrakis(,B-cyanoethyl) tin and 33.4 g. of hexakis(,6-cyan0ethyl)ditin, whichrepresented a yield of 92% based upon the tin lost by the cathode and a58.7% yield based on acrylonitrile converted.

Example Vlll In ml. of 50% aqueous ethanol containing 7.2 g. (0.18 mole)sodium hydroxide was suspended 10.02 g. (0.03 mole) oftetrakis(fl-cyanoethyDtin. As the mixture was refluxed, ammonia wasliberated and the suspended material gradually went into solution. Aftera reflux period of 5 6 hours, the solution was evaporated under reducedpressure and the remaining cream solid was carefully acidified with 20%hydrochloric acid with ice cooling. The remaining insoluble material wasfiltered, washed with water and dried at 20 C. at 1 mm. Hg.

The product, tetrakis(,8-carboxyethyl)tin, was obtained as a creamsolid, 9.2 g., which had an initial melting point, before and after fourrecrystallizations from water, of 112-113 C. The infrared and nuclearmagnetic resonance spectra were consistent with the above formula. Theelemental analysis was as follows.

Analysis calc., percent wt.: C, 35.2; H, 4.8; O, 31.2; Sn, 28.8. Found:C, 34.9; H, 4.8; O, 33.0; Sn, 27.8.

Example IX In 25 ml. of tetrahydrofuran Was suspended 2 g. of purifiedtetrakis(,B-carboxyethyDtin. An etheral solution of diazomethane wasslowly and carefully added to the suspension with occasional stirring.When the reaction was complete as evidenced by cessation of nitrogenevolution, the solvents were evaporated by exposure to a stream of airheated to 40 C. The liquid residue was dissolved in 25 ml. of ether andchromatographed over alumina. Evaporation of the solvent from the eluateafforded 1.9 g. of tetrakis(,G-carbomethoxylethyl)tin, the infrared andnuclear magnetic resonance spectrum of which were consistent with theabove formula: The elemental analysis was as follows.

' Analysis calc., percent wt.: C, 41.1; H, 6.0; Sn, 25.4. Found: C,41.0; H, 6.2; Sn, 24.0.

Example X To g. (0.0122 mole) of tetrakis(B-carboxyethyDtin was added22.2 g. (0.187 mole) of thionyl chloride. The mixture was placed in aflask and was agitated by the passage of a nitrogen stream, which streamalso served to remove the hydrogen chloride formed during reaction.After the reaction had proceeded at room temperature for 24 hours, anadditional 11.1 g. (0.0935 mole) of thionyl chloride was added. After'an additional 24 hours reaction time, a similar addition was made.After a total of 72 hours reaction time, infrared analysis indicated thereaction was complete and the excess thionyl chloride was evaporated toafford 5.4 g. of tetrakis(fl-chlorocarbonylethyl)tin, a tan liquid. Theinfrared spectrum of the prodnot was in good agreement with thatrequired for the above structure. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 29.8; H, 3.3; Cl, 29.4; Sn, 24.5.Found:.C, 29.1; H, 3.2; Cl, 30.4; Sn, 26.0.

Example XI 'ylethyl)tin. The mixture was allowed to stand overnight atroom temperatureand was then evaporated to remove the excess ethanol andpyridine. The residue was dissolved in 20 ml. of methylene chloride andthe solution was washed with two ml. portions of 10% hydrochloric acid,three 10 ml. portions of water, and was dried over anhydrous magnesiumsulfate. Evaporation of the solvent afforded a light yellow liquid whichwas dissolved in 20 ml. ether and chromatographed over alumina.Evaporation of the ether from the eluate yielded 1.3 g. oftetrakis(B-carbethoxyethyDtin, a light yellow liquid, the infrared andnuclear magnetic resonance spectra of which were consistent with theabove formula. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 45.4; H, 6.8; Sn, 22.8. Found: C, 45.0;H, 6.4; Sn, 21.6.

Example XII To 50 ml. of aqueous ammonia was added 2.5 g. (0.00515 mole)of tetrakis(fl-chlorocarbonylethyl)tin. After standing overnight atrefrigerator temperature, the mixture was evaporated to give a solidwhich was extracted with two 10 ml. portions of ethanol. The extract wasfiltered and evaporated to give 1.3 g. of tetrakis(,8-carbamidoethyl)tin, a hygroscopic solid. The infrared and nuclearmagnetic resonance spectra were in good agreement with those requiredfor the above structure.

Example XIII pressure gave tetrakis(' -aminopropyhtin, a yellow visconsliquid. The infrared spectrum of this liquid was consistent with theabove structure. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 41.1; H, 9.15; N, 15.95; Sn, 33.8.Found: C, 40.0; H, 8.9; N, 14.7; Sn, 31.0.

The amine was further characterized as the tetrakis picrate salt bytreating a solution of 3.5 g. (0.01 mole) of the tretrakis('-aminopropyDtin with a saturated solution of 9.2 g. (0.01 mole) ofpicric acid in 15 ml. of hot ethanol. On cooling and standing at roomtemperature for one day, crystals were obtained. Recrystallization from2:1 ethanol-ether afforded yellow crystals, M.P. 156-157", which was thepicrate salt of the amine.

Analysis calc., percent Wt.: C, 34.2; H, 3.5. Found: C, 34.4; H, 3.8.

Example XIV A suspension of 2.8 g. (0.005 mole) of hexakis(,6'-cyanoethyl)di-tin in 85% ml. of aqueous ethanol containing 1.2 g. (0.03mole) of sodium hydroxide was stirred at room temperature for four days.Evaporation of the solvent under reduced pressure gave a white,hygroscopic, glassy residue which was acidified with 10% hydrochloricacid with cooling and the resulting residue was extracted with three 50ml. portions of acetone. Evaporation of the acetone gave a clear, whitegum, a portion of which was crystallized in a 3:1 solution of ethylacetate-methylene chloride. The product, hexakis- (B-carboxyethyDdi-tinhad a melting point of 284-293 C. The infrared and nuclear magneticresonance spectra were consistent with the above structure. Elementalanalysis indicated that the product contained the hexakis(B-carboxylethyl)di-tin.

Example XV In 25 ml. of tetrahydrofuran was dissolved 1 g. of the impurehexakis(fl-carboxylethyDdi-tin product of Example XIV and the solutionwas treated with excess diazomethane in ether. Evaporation of thesolvent gave a yellow liquid which was dissolved in ether andchromatographed over alumina. Evaporation of the solvent from the eluategave hexakis(fl-carbomethoxyethyl)di-tin, a light yellow mobile liquid.The infrared and nuclear magnetic resonance spectra were consistent withthe above structure. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 38.0; H, 5.5; Sn, 32.1. Found: C, 38.8;H, 5.3; Sn, 29.0.

Example XVI A solution of 5.6 g. (0.01 mole) ofhexakisQQ-cyanoethyl)di-tin in 200 ml. of tetrahydrofuran was added to asuspension of 3.42 g. (0.09 mole) of lithium aluminum hydride in 250 ml.of tetrahydrofuran. The mixture was stirred at 55 C. for 1 day, cooledand treated with 18 ml. of water. After the mixture was stirred for onehour, the upper layer was removed by decantation and was evaporatedunder high vacuum to give 3.2 g. of a clear viscous oil which was onlysparingly soluble in acetonitrile, dichloromethane and chloroform. Theoil was dis solved in methanol and the solution was filtered to removesuspended material. Evaporation of solvent affordedhexakisOy-aminopropyl)di-tin, a clear oil which possessed acharacteristic amine odor. The infrared s ectrum was in good agreementwith that required for hexakis('yaminopropyl)di-tin. The elementalanalysis was as follows.

Analysis calc., percent wt.: C, 37.0; H, 8.2; N, 14.4. Found: C, 38.6;H, 9.1; N, 11.3.

I claim as my invention:

1. The process of producing B-carboxyethyl tin compounds byelectrolyzing an aqueous solution of acrylonitrile having a pH fromabout 7 to about 9.5 in the presence of a tin cathode, said electrolysisbeing conducted at a cathode reference potential from about 1.6 volt toabout 2.0 volt vs. the saturated cal-omel electrode; hydrolyzing theresulting per(/3-cyanoethy1)monoto di-tin by contacting with strongbase; and neutralizing the resulting basic solution to affordper(,8-carboxyethyl) monoto di-tin.

2. The process of producing hexakis(B-carboxyethyl) ditin byelectrolyzing aqueous acrylonitrile solution having an acrylonitrileconcentration from about by weight to about by weight based on totalsolution and a pH from about 7 to about 9.5, in the presence of a tincathode, said electrolysis being conducted at a cathode referencepotential from about 1.6 volt to about 2.0 volt vs. the saturatedcalomel electrode; hydrolyzing the resulting hexakis(,6-cyanoethyl)ditinby contacting with aqueous strong base; and neutralizing the resultingbasic solution to afford hexakis(fi-carboxyethyl) di-tin.

3. The process of producing ,B-cyanoethyl tin compounds by electrolyzingan aqueous solution of acrylonitrile having a pH from about 7 to about9.5 in the presence of a tin cathode, said electrolysis being conductedat a cathode reference potential from about 1.6 volt to about -2.0 voltvs. the saturated calomel electrode.

4. The process of producing tetrakis(B-cyanoethyl)tin by electrolyzingaqueous acrylonitrile solution having an acrylonitrile concentrationfrom about 17% by weight to about 25% by weight based on total solutionand a pH from about 7 to about 9.5, in the presence of a tin cathode,said electrolysis being conducted at a cathode reference potential fromabout 1.6 volt to about -2.0 volt vs. the saturated calomel electrode.

5. The process of producing tetrakis(fl-cyanoethyl)tin by electrolyzingan aqueous acrylonitrile solution having an acrylonitrile concentrationfrom about 17% by weight to about 25% by weight based on total solutionand a pH from about 7.5 to about 9, at a temperature from about 20 C. toabout 30 C., in the presence of a tin cathode and an inert anode, saidelectrolysis being conducted at a cathode reference potential from about1.7 volt to about -1.9 volt vs. the saturated calome l electrode.

6. The process of producing hexakis(,B-cyanoethyDditin by electrolyzingan aqueous acrylonitrile solution having an acrylonitrile concentrationfrom about 5% by weight to about 15% by weight based on total solutionand a pH from about 7 to about 9.5, in the presence of a tin cathode,said electrolysis being conducted at a cathode 12 reference potentialfrom about -1.6 volt to about 2.0 volts vs. the saturated calomelelectrode.

7. The process of producing htixalrisUi-cyanoethyl)ditin byelectrolyzing an aqueous acrylonitrile solution havan an acrylonitrileconcentration from about 5% by weight to about 15% by weight based ontotal solution and a pH from about 7.5 to about 9, at a temperature fromabout 5 C. to about 15 C., in the presence of a tin cathode and an inertanode, said electrolysis being conducted at a cathode potential fromabout -1.7 volt to about 1.9 volt vs. the saturated cal'omel electrode.

8. Per(fi-X-ethyl)monoto di-tin wherein X is selected from the groupconsisting of aminomethy-l, halocarbonyl, carboxy, carboalkoxy whereinthe alkyl is alkyl of from 1 to 8 carbon atoms, carbamido,N-alkylcarbamido wherein the alkyl is alkyl of from 1 to 8 carbon atoms,and N,N-dialkyl-carbamido wherein the a-lkyls independently are alkyl offrom 1 to 8 carbon atoms.

9. Per(,B-carboxyethyl)monoto di-tin.

10. Tetrakis fi-carb oxyethyl) tin.

11. Hexakis(,8-carboxyethyl)di-tin.

12. Per(/3-halocarbonylethyl)monoto di-tin wherein the halogen moiety ishalogen of atomic number from 17 to 35.

13. Tetrakis B-chlorocarb onylethyl) tin.

14. Per('y-arninopropyl)monoto di-tin.

15. Tetrakis('y-aminopropyDtin.

16. Hexakis(' -aminopropyl)di-tin.

17. Per(,8-carboalkoxyethyl)monoto di-tin wherein the alkyl moieties arealkyl of from 1 to 8 carbon atoms.

18. Tetrakis(B-carboalkoxyethyDtin wherein the alkyl moieties are alkylof from 1 to 8 carbon atoms.

19. Tetrakis fi-carb omethoxyethyl) tin.

20. Hexakis(B-cyanoethyl)di-tin.

References Cited Bencowitz: Chem. Abstracts, vol. 54 (1960), page7374(i).

TOBIAS E. LEVOW, Primary Examiner,

W. F. W. BELLAMY, Assistant Examiner.

1. THE PROCESS OF PRODUCING B-CARBOXYETHYL TIN COMPOUNDS BYELECTROLYZING AN AQUEOUS SOLUTION OF ACRYLONITRILE HAVING A PH FROMABOUT 7 TO ABOUT 9.5 IN THE PRESENCE OF A TIN CATHODE, SAID ELECTROLYSISBEING CONDUCTED AT A CATHODE REFERENCE POTENTIAL FROM ABOUT -1.6 VOLT TOABOUT -2.0 VOLT VS. THE SATURATED CALOMEL ELECTRODE; HYDROLYZING THERESULTING PER(B-CYANOETHYL)MONOTO DI-TIN BY CONTACTING WITH STRONG BASE;AND NEUTRALIZING THE RESULTING BASIC SOLUTION TO AFFORDPER(B-CARBOXETHYL) MONO- TO DI-TIN.